Frame generating apparatus and frame generating method

ABSTRACT

A frame generating apparatus accommodating a client signal in an optical data transfer unit frame with a higher bit rate than the client signal includes a deserializer, a plurality of generic mapping procedure circuits, and a serializer. The deserializer deserializes the client signal into parallel signals, the number of parallel signals corresponding to the number of tributary slots used in the optical data transfer unit frame. The plurality of generic mapping procedure circuits inserts data and stuff into a frame accommodating portion of the optical data transfer unit frame based on a difference in the bit rate between the client signal and the optical data transfer unit frame. The serializer serializes the parallel signals output from the plurality of generic mapping procedure circuits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is notice that there is more than one application for reissue ofU.S. Pat. No. 8,675,684. This application is an application for reissueof application Ser. No. 12/719,277, which issued as U.S. Pat. No.8,675,684 on Mar. 18, 2014. U.S. Pat. No. 8,675,684 is based upon andclaims the benefit of priority of the prior Japanese Patent ApplicationNo. 2009-55448, filed on Mar. 9, 2009, the entire contents of which areincorporated herein by reference. A second application was filed on Jan.17, 2018 and is assigned application Ser. No. 15/874,448. The secondapplication is a continuation reissue of application Ser. No.15/072,838, which is an application for reissue of U.S. Pat. No.8,675,684.

FIELD

The present invention relates to a frame generating apparatus and aframe generating method.

BACKGROUND

In optical networks applying wavelength division multiplexing (WDM), anoptical transport network (OTN) has been standardized as a framework. Inthe OTN, a plurality of types of client signals may be accommodated, andlarge-volume transmission may be performed. Japanese Laid-open PatentPublication No. 2008-113394 discloses an optical transmission system inwhich client signals are transmitted while being accommodated ormultiplexed in optical transfer unit (OTU) frames in the OTN.

A difference in bit rate between an accommodated signal and a framesignal that accommodates the signal is compensated by asynchronouslymapping the accommodated signal to the frame signal (asynchronousmapping procedure (AMP)). However, with an increase in bit rate anddiversification of accommodated signals, generic mapping procedure (GMP)is being adopted. In the GMP, the number of pieces of data and thenumber of pieces of stuff to be accommodated in a frame accommodatingportion are determined based on a difference in bit rate between anaccommodated signal and a frame signal that accommodates the signal. TheGMP is disclosed in U.S. Pat. No. 7,020,094.

For adopting the GMP and accommodating a frame signal that accommodatesa signal in a frame signal having a bit rate higher than that of theframe signal, generation of optical data transfer unit (ODTU) frames isrequired.

SUMMARY

According to an aspect of an embodiment, a frame generating apparatusfor accommodating a client signal in an optical data transfer unit framewith a higher bit rate than the client signal includes a deserializer, aplurality of GMP circuits, and a serializer. The deserializerdeserializes the client signal into parallel signals, the number ofparallel signals corresponding to the number of tributary slots used inthe optical data transfer unit frame. The plurality of GMP circuitsinserts data and stuff into a frame accommodating portion of the opticaldata transfer unit frame based on a difference in bit rate between theclient signal and the optical data transfer unit frame. The serializerserializes the parallel signals output from the plurality of GMPcircuits.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a signaltransmitting/receiving apparatus to which a frame generating sectionaccording to an embodiment is applied;

FIG. 2 is a diagram illustrating a format of an OTU frame;

FIG. 3 is a diagram illustrating main types of client signals to beaccommodated in OTU4/ODU4/OPU4;

FIGS. 4A and 4B are diagrams illustrating an example of a framestructure of OTU4/ODU4/OPU4 when multiplexing and accommodating aplurality of ODUj's;

FIG. 5 is a diagram illustrating a process performed by regarding twoframes as one unit;

FIG. 6 is a diagram illustrating mapping when an ODU0 signal isaccommodated in ODU4;

FIG. 7 is a diagram illustrating mapping when an ODU1 signal isaccommodated in ODU4;

FIG. 8 is a diagram illustrating mapping when an ODU2 or ODU2e signal isaccommodated in ODU4;

FIG. 9 is a diagram illustrating mapping when an ODU3 signal isaccommodated in ODU4;

FIG. 10 is a block diagram illustrating details of the frame generatingsection;

FIGS. 11A and 11B are block diagrams illustrating a GMP processingsection;

FIGS. 12A and 12B are diagrams illustrating addresses assigned to aframe accommodating portion of an ODTU frame;

FIG. 13 is a diagram illustrating stuff bytes inserted into a signalaccommodating portion in accordance with an expression;

FIGS. 14A and 14B are diagrams illustrating storage of information forGMP in an ODTUOH unit;

FIG. 15 is a diagram illustrating an example of an OPUkOH unit; and

FIG. 16 is a diagram illustrating another example of an OPUkOH unit.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment will be described with reference to theaccompanying drawings.

FIG. 1 is a block diagram illustrating a configuration of a signaltransmitting/receiving apparatus 1000 which includes a frame generatingsection 100 according to an embodiment. The signaltransmitting/receiving apparatus 1000 includes the frame generatingsection 100, a plurality of optical transmission/reception interfacesections 200, and a network-side optical transmission/receptioninterface section 300.

The frame generating section 100 receives client signals via the opticaltransmission/reception interface sections 200 and generates OTU frames.Here, an input/output section of each of the opticaltransmission/reception interface sections 200 is called a tributaryport. The signal transmitting/receiving apparatus 1000 includes “n”number of tributary ports t. The OTU frames generated by the framegenerating section 100 are transmitted to a network via the opticaltransmission/reception interface section 300. On the other hand, theframe generating section 100 receives OTU frames via the opticaltransmission/reception interface section 300. The frame generatingsection 100 extracts client signals from the received OTU frames. Theextracted client signals are transmitted to the outside via the opticaltransmission/reception interface sections 200.

FIG. 2 is a diagram illustrating a format of an OTU frame. The OTU frameincludes an overhead unit, an optical channel payload unit (OPUk), andan optical channel transport unit forward error correction-overhead(OTUk FEC-OH).

The overhead unit has a frame size of 16 bytes×4 rows in the 1st to 16thcolumns, and is used for connection and quality management. The OPUk hasa frame size of 3808 bytes×4 rows in the 17th to 3824th columns, andaccommodates client signals for providing one or more services. The OTUkFEC-OH has a frame size of 256 bytes×4 rows in the 3825th to 4080thcolumns, and is used to correct errors that may occur duringtransmission.

By adding overhead bytes used for connection and quality management tothe OPUk, an optical channel data unit (ODUk) is generated. Also, byadding overhead bytes used for frame synchronization, connection,quality management, etc. and the OTUk FEC-OH to an ODUj unit, an opticalchannel transport unit (OTUk) is generated.

In this embodiment, a description will be given about generation of OTNframes for accommodating and transmitting an ETHERNET signal having abit rate of 100 Gbps and various signals that may be accommodated in theconventional OTN. Hereinafter, OTN frames corresponding to 100 Gbps arecalled OTU4/ODU4/OPU4.

FIG. 3 is a diagram illustrating main types of client signalsaccommodated in the OTU4/ODU4/OPU4. A 100 Gb ETHERNET (hereinafterreferred to as 100 GbE) having a bit rate of 103.125 Gbps isaccommodated in a payload unit of the OTU4/ODU4/OPU4 without beingmultiplexed. ODU3, ODU2, and ODU1, which are ODUj described in ITU-T G.709 as an existing OTN frame, or ODU2e described in ITU-T G. supplement43 is accommodated in the payload unit of the OTU4/ODU4/OPU4 by beingmultiplexed.

FIGS. 4A and 4B are diagrams illustrating an example of a framestructure of the OTU4/ODU4/OPU4 when accommodating a plurality of ODUj(j=0, 1, 2, 2e, 3, 3e1, and 3e2) by multiplexing. The frame generatingsection 100 inserts first fixed stuff bytes of 8+40n (“n” is an integerof 0 or more) bytes×4 rows into the payload unit of OPU4.

In FIGS. 4A and 4B, it is assumed that n=0 for simplifying thedescription. 80 types of tributary slots realize a bit rate of 100 Gbps.The bit rate of each tributary slot is 1.301709251 Gbps.

Referring to FIG. 4A, the frame generating section 100 inserts the firstfixed stuff bytes into 8 columns×4 bytes in the 3817th to 3824th columnsin an ODU4 frame. The frame generating section 100 accommodates, in anarea other than the first fixed stuff bytes in each OPU4 frame, 47.5sets of tributary slots, each set including 80 types of tributary slotsin which 1 byte×4 rows is one unit. The frame generating section 100accommodates 48 sets of tributary slots 1 to 40 and 47 sets of tributaryslots 41 to 80 in an odd-numbered OTU frame. Also, the frame generatingsection 100 accommodates 47 sets of tributary slots 1 to 40 and 48 setsof tributary slots 41 to 80 in an even-numbered OTU frame. The framegenerating section 100 performs a process by regarding 80 types of OTUframes as one multi-frame cycle when accommodating a plurality of typesof signals in OTU frames.

In an odd-numbered OTU frame, a tributary slot 1 (Tribslot#1) isassigned to the 17th, 97th, . . . , and 3777th columns in an ODUj frame.In an even-numbered OTU frame, a tributary slot 1 (Tribslot#1) isassigned to the 57th, 137th, . . . , and 3737th columns in an ODUjframe. Also, in an odd-numbered OTU frame, a tributary slot 80(Tribslot#80) is assigned to the 96th, 176th, . . . , and 3776th columnsin an ODUj frame. In an even-numbered OTU frame, a tributary slot 80(Tribslot#80) is assigned to the 56th, 136th, . . . , and 3816th columnsin an ODUj frame.

As illustrated in FIG. 4B, the column size of tributary slots varies ineach frame. Specifically, 48 columns of tributary slots #1 to #40 areaccommodated in an odd-numbered OTU frame, and 47 columns of tributaryslots #1 to #40 are accommodated in an even-numbered OTU frame. On theother hand, 47 columns of tributary slots #41 to #80 are accommodated inan odd-numbered OTU frame, and 48 columns of tributary slots #41 to #80are accommodated in an even-numbered OTU frame. Thus, in thisembodiment, a process is performed by regarding two frames as one unit,as illustrated in FIG. 5. Accordingly, the column size of each unit maybe the same.

Next, a description will be given about mapping when accommodating anODUj signal in ODU4. FIG. 6 is a diagram illustrating mapping whenaccommodating an ODU0 signal in ODU4. Referring to FIG. 6, the framegenerating section 100 uses one set of tributary slots whenaccommodating one ODU0 signal in ODU4.

FIG. 7 is a diagram illustrating mapping when accommodating an ODU1signal in ODU4. Referring to FIG. 7, the frame generating section 100uses two sets of tributary slots when accommodating one ODU1 signal inODU4.

FIG. 8 is a diagram illustrating mapping when accommodating an ODU2signal or an ODU2e signal in ODU4. Referring to FIG. 8, the framegenerating section 100 uses eight sets of tributary slots whenaccommodating one ODU2 or ODU2e signal in ODU4.

FIG. 9 is a diagram illustrating mapping when accommodating an ODU3signal in ODU4. Referring to FIG. 9, the frame generating section 100uses thirty-one sets of tributary slots when accommodating one ODU3signal in ODU4. Additionally, when accommodating an ODUj signal in ODU4by using an arbitrary number of sets of tributary slots, the mappingdescribed above may be applied.

Next, details of the frame generating section 100 will be described.FIG. 10 is a block diagram illustrating the details of the framegenerating section 100. Referring to FIG. 10, the frame generatingsection 100 includes a plurality of ODUj processing sections 10, a GMPprocessing section 20, a plurality of ODTU processing sections 30, anODTUG4 processing section 40, an OPU4 processing section 50, an ODU4processing section 60, and an OTU4 processing section 70.

Each of the ODUj processing sections 10 receives a client signal, whichis an accommodated signal, from the corresponding opticaltransmission/reception interface section 200. The GMP processing section20 determines the number of pieces of data and the number of pieces ofstuff to be accommodated in a frame accommodating portion based on adifference between a bit rate of an accommodated signal and a bit rateof a frame signal that accommodates the signal, and inserts the piecesof data and the pieces of stuff into the frame accommodating section.The details will be described below.

Each of the ODTU processing sections 30 generates an ODTU frame from theframe signal in which data and stuff have been inserted in the GMPprocessing section 20. The ODTUG4 processing section 40 multiplexes theODTU frames generated in the respective ODTU processing sections 30,thereby generating an ODTUG4 frame. The OPU4 processing section 50generates an OPU4 frame from the ODTUG4 frame. The ODU4 processingsection 60 generates an ODU4 frame from the OPU4 frame. The OTU4processing section 70 generates an OTU4 frame from the ODU4 frame andtransmits the OTU4 frame to the optical transmission/reception interfacesection 300.

FIGS. 11A and 11B are block diagrams illustrating the details of the GMPprocessing section 20. The GMP processing section 20 includes adeserializer 21, a plurality of GMP processing circuits 22, and aserializer 23. The deserializer 21 interleaves an ODUj signal in unitsof bytes. In this embodiment, the deserializer 21 deserializes the ODUjsignal into parallel signals, the number of which corresponds to thenumber of tributary slots used in an ODTU frame. That is, thedeserializer 21 parallelizes the ODUj signal in units of tributaryslots. The number of GMP processing circuits 22 included in the GMPprocessing section 20 corresponds to the number of tributary slots. Inthis embodiment, 80 types of tributary slots are used and thus the GMPprocessing section 20 includes 80 GMP processing circuits 22.

In this case, the operation speed required for each of the GMPprocessing circuits 22 is equivalent to or lower than the bit rate ofthe ODTU frame in which the ODUj signal is accommodated. In thisembodiment, the operation speed required for each of the GMP processingcircuits 22 may be about 1.25 Gbps. A bit rate deviation is the same inall the channels after the deserializer 21, and thus a Cn value for GMPis the same. Therefore, for mapping ODUj signal into ODTU frame that isoccupied by m tributary slots of OTU, m GMP processing circuits use thesame Cn value.

The GMP processing circuit 22 inserts data into a frame accommodatingportion of an ODTU frame when the following expression (1) is satisfied,and inserts stuff into the frame accommodating portion when thefollowing expression (2) is satisfied.N×Cn mod(the total number of bytes in a signal accommodating portion)<Cn  (1)N×Cn mod(the total number of bytes in a signal accommodating portion)≥Cn  (2)

N: an address assigned to the frame accommodating portion of the ODTUframe

Cn: (the bit rate of the ODUj signal)/(the bit rate of the ODTUframe)×(the total number of bytes in the frame accommodating portion ofthe ODTU frame)

mod: an operator for calculating a remainder (modulo)

In this case, the number of pieces of stuff to be inserted into thesignal accommodating portion of the ODTU frame may be calculated bysubtracting Cn from the total number of bytes in the signalaccommodating portion. Next, the number of pieces of stuff when theabove expression (2) is satisfied will be described. For example, adescription will be given about accommodating ODU0 in OPU4 by using oneset of tributary slots (TS). In this case, the total number of bytes (B)in the signal accommodating portion in 1TS is 15200. The number of TS's(Nts) used for accommodation is 1. The bit rate (fc) of ODU0 is1.244160000 Gbps (typical value). The bit rate (fs) of 1TS in OPU4 is1.301709251 (typical value). Thus, the number of bytes to beaccommodated Cn is 14528 according to the following expression (3). Inexpression (3), “Int” indicates rounding up the number after the decimalpoint.Cn=Int((fc/Nts)/fs×B)=Int(1.244160000/1)/1.301709251×15200)=14528   (3)

The above example shows mapping ODUj (j=0) into ODTU with a tributaryslot occupation of OTU. For the case of mapping ODUj into ODTU that isoccupied m tributary slots of OTU, m GMP processing circuits are useswith same Cn value. Therefore, data of ODUj or stuff are inserted intoODTU frame with m granularity manner.

Next, addresses assigned to the frame accommodating portion of the ODTUframe will be described with reference to FIGS. 12A and 12B. Theaddresses are sequentially assigned in accordance with the number ofTS's in each row of each signal accommodating portion. Referring to FIG.12A, when the number of TS's is 1, addresses are sequentially assignedin each row of the signal accommodating portion.

Referring to FIG. 12B, when the number of TS's is 4, addresses aresequentially assigned in units of four columns in each row of the signalaccommodating portion. Specifically, addresses 1A to 1D for tributaryslots A to D, where A<B<C<D, are sequentially assigned to the 1st to 4thcolumns of the signal accommodating portion. Likewise, addresses 2A to2D for tributary slots A to D, where A<B<C<D, are sequentially assignedto the 5th to 8th columns of the signal accommodating section. That is,when “n” number of TS's is used, addresses are assigned to concatenateODTU of 1TS by n.

FIG. 13 is a diagram illustrating stuff bytes inserted into the signalaccommodating portion in accordance with the above expression (2). InFIG. 13, “S” corresponds to a stuff byte. As illustrated in FIG. 13,stuff bytes are inserted into the signal accommodating portion in adispersed manner. Accordingly, jitter may be effectively suppressed whenstuff bytes are removed in a receiver side compared to when stuff bytesare continuously inserted.

FIGS. 14A and 14B are diagrams illustrating storage of information forGMP in an ODTU OH unit. Referring to FIG. 14A, when 1TS is used,overhead information for the TS is given to an ODTU frame. Referring toFIG. 14B, when 4TS (TS#A to #D, where A<B<C<D) is used, overheadinformation for each TS is given to an ODTU frame. The overheadinformation includes information about the number of pieces of stuffcalculated in the above expression (2). The information about the numberof pieces of stuff is the same in the overhead corresponding to each TS.

FIG. 15 is a diagram illustrating an example of an OPUk OH unit.Referring to FIG. 15, an OTU4/ODU4/OPU4 frame stores, in the 15th columnand the 4th row, information indicating the correspondence betweentributary slot numbers and tributary ports. Specifically, theOTU4/ODU4/OPU4 frame stores a signal for identifying port numbers of 80tributary slots using seven bits. Accordingly, the number of tributaryslots used for accommodating an ODUj signal in the OTU4/ODU4/OPU4 framemay be determined.

FIG. 16 is a diagram illustrating another example of the OPUk OH unit.The difference from the example illustrated in FIG. 15 is that theOTU4/ODU4/OPU4 frame stores, in the 15th column and the 3rd row, typesof client signals accommodated in respective tributary slots (ODU0,ODU1, ODU2, ODU3, and ODU2e). By having this type of OH, the types ofaccommodated client signals may be identified.

In this embodiment, a description has been given about frame generationfor transmitting a client signal having a bit rate under 100 Gbps at abit rate of 100 Gbps. However, this embodiment is not limited thereto.This embodiment may also be applied to frame generation for transmittinga low-bit-rate client signal at a higher bit rate. In this case, too, anoperation speed required for a GMP circuit may be decreased bydeserializing a client signal into parallel signals the number of whichcorresponds to the number of multiple frames of an ODTU frame.

In this embodiment, the number of tributary slots in each set is 80, butthe number is not limited thereto. In this case, when the number of GMPprocessing circuits 22 is the same as the number of tributary slots ineach set, an advantage of this embodiment may be obtained.

An embodiment of the present invention has been described in detail. Thepresent invention is not limited to this specific embodiment, andvarious modifications and changes are acceptable within the scope of thepresent invention described in the following claims.

According to the frame generating apparatus and frame generating methoddisclosed in the specification, ODTU frames applicable to the GMP methodmay be generated.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiments of the presentinvention have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A frame generating apparatus that accommodates aclient signal in an optical data transfer unit frame with a higher bitrate than the client signal, the frame generating apparatus comprising:a deserializer that deserializes the client signal into M parallelsignals where M is corresponding to the number of tributary slots usedin the optical data transfer unit frame; M generic mapping procedurecircuits that inserts data and stuff into a frame accommodating portionof the optical data transfer unit frame based on a difference in the bitrate between the client signal and the optical data transfer unit frame;and a serializer that serializes the M parallel signals output from Mgeneric mapping procedure circuits, wherein M generic mapping procedurecircuits that in accordance with an address inserts data into the frameaccommodating portion of the optical data transfer unit frame when afirst expression (N×Cn) mod Tb<Cn is satisfied, and inserts stuff intothe frame accommodating portion of the optical data transfer unit framewhen a second expression (N×Cn) mod Tb≥Cn is satisfied, “N” representingthe address assigned to the frame accommodating portion of the opticaldata transfer unit frame, “Cn” representing (a bit rate of the clientsignal)÷(a bit rate of the optical data transfer unit frame)×(the totalnumber of bytes in the frame accommodating portion of the optical datatransfer unit frame),“Tb” representing the total number of bytes in asignal accommodating portion, and “mod” representing a remainderoperator.
 2. The frame generating apparatus according to claim 1,further comprising: an optical data transfer unit generatoraccommodating a signal from the serializer in the optical data transferunit frame, wherein the frame accommodating portion includes a pluralityof rows, and wherein the optical data transfer unit generatorsequentially assigns addresses in accordance with the number oftributary slots in each row of the frame accommodating portion.
 3. Theframe generating apparatus according to claim 2, wherein the opticaldata transfer unit generator accommodates the signal from the serializerin the optical data transfer unit frame by regarding two types ofoptical data transfer unit frames of eighty types of optical datatransfer unit frames as one set and forty sets of the optical datatransfer unit frames as one multi-frame cycle.
 4. A frame generatingmethod for accommodating mapping a client signal in into an optical datatransfer unit frame with a higher bit rate than the client signal, themethod comprising: mapping a group of M successive bytes of the clientsignal into a group of M successive bytes of the optical data transferunit frame, where M is the number of tributary slots of the optical datatransfer unit frame; deserializing, by an apparatus, the client signalinto parallel signals, the number of parallel signals corresponding tothe number of tributary slots used in the optical data transfer unitframe; inserting, by an apparatus, data and stuff into a frameaccommodating portion of the optical data transfer unit frame based on adifference in bit rate between the client signal and the optical datatransfer unit frame; and serializing, by an apparatus, the parallelsignals after inserting data and stuff into the frame accommodatingportion of the optical data transfer unit frame, wherein data isinserted inserting data into the a frame accommodating portion of theoptical data transfer unit frame in accordance with an address when afirst expression (N×Cn) mod Tb<Cn is satisfied, and inserting stuff isinserted into the frame accommodating portion in accordance with anaddress when a second expression (N×Cn) mod Tb>Cn Tb≥Cn is satisfied,“N” representing the address assigned to the frame accommodating portionof the optical data transfer unit frame, “Cn” representing (a bit rateof the client signal)÷(a bit rate of the optical data transfer unitframe)×(the a total number of bytes in the frame accommodating portionof the optical data transfer unit frame), “Tb” representing the totalnumber of bytes in a signal accommodating portion the frameaccommodating portion of the optical data transfer unit frame, and “mod”representing a remainder operator.
 5. The method according to claim 4,wherein the stuff is inserted into the frame accommodating portion ofthe optical data transfer unit frame in a dispersed manner.
 6. Themethod according to claim 4, further comprising: accommodating a signalfrom the serializer the data or the stuff in the frame accommodatingportion of optical data transfer unit frame, wherein the frameaccommodating portion includes a plurality of rows, and whereinaddresses are sequentially assigned in accordance with the number oftributary slots in each row of the frame accommodating portion inaccommodating the signal from the serializer.
 7. The method according toclaim 6, wherein accommodating the signal from the serializer in data orthe stuff in the frame accommodating portion of the optical datatransfer unit frame by regarding two types of optical data transfer unitframes of eighty types of optical data transfer unit frames as one setand forty sets of the optical data transfer unit frames as onemulti-frame cycle.
 8. The method according to claim 4, furthercomprising: generating an optical transfer unit frame by multiplexingthe plurality of optical data transfer unit frames, wherein tributaryslots have corresponding tributary port numbers, and wherein thetributary port numbers corresponding to tributary slots are stored in anoptical channel payload unit overhead in generating an optical transferunit frame.
 9. The method according to claim 8, wherein a type of theclient signal is further stored in the optical channel payload unitoverhead in generating an optical transfer unit frame.
 10. A framegenerating apparatus comprising: a deserializer that deserializes aclient signal into parallel signals, the number of parallel signalscorresponding to the number of tributary slots used in a an optical datatransfer unit frame; and a plurality of generic mapping procedurecircuits that in accordance with an address inserts data into a frameaccommodating portion of the optical data transfer unit frame when afirst expression (N×Cn) mod Tb<Cn is satisfied, and inserts stuff intothe frame accommodating portion of the optical data transfer unit framewhen a second expression (N×Cn) mod Tb≥Cn is satisfied, “N” representingthe address assigned to the frame accommodating portion of the opticaldata transfer unit frame, “Cn” representing (a bit rate of a clientsignal)÷(a bit rate of the optical data transfer unit frame)÷×(the totalnumber of bytes in the frame accommodating portion of the optical datatransfer unit frame), “Tb” representing the total number of bytes in asignal accommodating portion, and “mod” representing a remainderoperator.
 11. A frame generating apparatus that accommodates a clientsignal in an optical data transfer unit frame with a higher bit ratethan the client signal, the frame generating apparatus comprising: ageneric mapping procedure circuit that inserts data or stuff into aframe accommodating portion of the optical data transfer unit framebased on a difference in the bit rate between the client signal and theoptical data transfer unit frame and maps a group of M successive bytesof the client signal into a group of M successive bytes of the opticaldata transfer unit frame, where M is the number of tributary slots ofthe optical data transfer unit frame; and wherein the generic mappingprocedure circuit that in accordance with an address inserts data intothe frame accommodating portion of the optical data transfer unit framewhen a first expression (N×Cn) mod Tb<Cn is satisfied, and inserts stuffinto the frame accommodating portion of the optical data transfer unitframe when a second expression (N×Cn) mod Tb≥Cn is satisfied, “N”representing the address assigned to the frame accommodating portion ofthe optical data transfer unit frame, “Cn” representing (a bit rate ofthe client signal)+(a bit rate of the optical data transfer unitframe)×(the total number of bytes in the frame accommodating portion ofthe optical data transfer unit frame), “Tb” representing the totalnumber of bytes in a signal accommodating portion, and “mod”representing a remainder operator.
 12. The frame generating apparatusaccording to claim 11, wherein the client signal is optical data unit(ODU) and the optical data transfer unit frame is optical data transferunit (ODTU).
 13. The frame generating apparatus according to claim 11,wherein the optical data transfer unit frame is optical data payloadunit (OPU) and the client signal is a signal with a lower bit rate thanthe OPU.
 14. The frame generating apparatus according to claim 11,wherein the optical data transfer unit frame is optical data payloadunit (OPU) and the client signal is Ethernet signal.
 15. The framegenerating apparatus according to claim 11, wherein the generic mappingprocedure circuits insert stuff into the frame accommodating portion ofthe optical data transfer frame in a dispersed manner.
 16. The framegenerating apparatus according to claim 11, further comprising: anoptical data transfer unit generator accommodating a client signal inthe optical data transfer unit frame, wherein the frame accommodatingportion includes a plurality of rows, and wherein the optical datatransfer unit generator sequentially assigns addresses in accordancewith M in each row of the frame accommodating portion, where M is thenumber of tributary slots of the optical data transfer unit frame. 17.The frame generating apparatus according to claim 11, furthercomprising: an optical frame unit frame generator generating an opticaltransfer unit frame, wherein tributary slots have correspondingtributary port numbers, and wherein the optical transfer unit framegenerator stores the tributary port numbers corresponding to thetributary slots in an optical channel payload unit overhead.
 18. Theframe generating apparatus according to claim 17, wherein the opticaltransfer unit frame generator further stores a type of the client signalin the optical channel payload unit overhead.